What I'm actually doing is walking through a storm drainage tunnel that stretches from just south of a nondescript parking lot here, under Interstate 15, under Caesar's and then the Las Vegas Strip, and then ends at the garage of the Imperial Palace.

At this moment, I'm in the care of Matt O'Brien, the 36-year-old news editor of the Las Vegas CityLife, who has just published , a chronicle and examination of the tunnels that most people, let alone Sin City residents, don't know exist.

O'Brien has generously offered to give me a tour of the section of the tunnel that snakes under Caesar's, since here I'm in town at the beginning of my Road Trip around the Southwest. But nothing he told me ahead of time has helped me keep my feet dry.

And even O'Brien, a longtime veteran of these tunnels, worries about his footwear.

"I don't like to mess up my shoes," he says after switching into a pair of beat-up old boots. "A couple of times, I've worn my Chuck Taylors and they got (messed) up, and I can't have that."

O'Brien, a former scholarship college basketball player from Georgia, first discovered the tunnels after a famous murder case in town in which the suspect, Timmy "T.J." Weber, avoided a police dragnet by wandering through the drainage system. The local newspaper had mentioned this element in a single paragraph, and O'Brien's interest was piqued.

So, being an editor and not having a lot of time to investigate, he assigned Josh Ellis, a freelance writer, to do a story on the tunnels. Ellis took a quick trip there, and then said he required rides to return, and didn't have his own car. So, O'Brien began driving Ellis to the tunnels and the two began regular visits down below.

"I'm a writer," O'Brien says, "and I thought there was a story. That's what got me down here."

Soon, they had produced a two-part series on the tunnels, and on the community of homeless people and graffiti artists who frequented them. Ellis moved on, and O'Brien began working on his book. It was published in June.

Now, he and I, and a friend of his, are wandering through the tunnels in the middle of a scorching Vegas July day, and you'd never know it was 110 degrees or more outside. In here, it's dark and cool--and wet.

That's not saying anything about how wet it can get in these tunnels if it rains. After all, these are the storm drainage tunnels that were built around 1977 as a way to control runoff from the local wash. Prior to that, O'Brien tells me, there are famous stories of cars washing up in culverts around town. With Vegas starting to expand, it was decided that the city needed a subtler way to deal with the results of storms.

So, here it is 2007, and there are currently 450 miles of these flood channels in town, including 300 miles underground. O'Brien says that the Las Vegas master plan created in the 1990s calls for around 1,000 miles of them within 20 or 25 years.

Most of the time, the tunnels are relatively dry, largely because it doesn't rain much in Vegas. But when it does, O'Brien says, the water level in the tunnels can rise rapidly, quickly turning into a flash flood. It's not where you'd want to be if such a thing were to happen.

In fact, spray painting--the graffiti kind--is a major element in the tunnels. Everywhere you look there is some kind of graffiti, much of it meaningless and uninteresting. But in some places, it turns into art.

Indeed, one of O'Brien's favorite places in the tunnel that he took me to is called "the art gallery," he says, and it's easy to see why. Everywhere you look, the walls are covered with colorful, artistic tagging, one beautiful image on top of another. On one wall, a lovely figure of a woman is sporting an orange halo. Elsewhere, the tags have more and more flair.

But don't expect to see what I saw--the taggers will likely cover it with new stuff any moment.